The present invention relates to a process for the preparation of trisphenol methanes.
Certain pharmaceutical hydroxyl-containing triaryl methanes and their preparation are disclosed in U.S. Pat. No. Re. 31,467. Other generic references to triaryl methane compounds include U.S. Pat. Nos. 877,053; 3,449,418; 3,739,000; and 4,048,200. It is generally well-known that trisphenolics can be prepared by condensing an alkoxy-substituted aromatic aldehyde or an alkoxy-substituted aromatic ketone with an excess of a substituted or unsubstituted phenol. See, e.g., U.S. Pat. Nos. 2,116,827; 3,787,451; and 4,394,496. U.S. Pat. No. 3,579,542 teaches the preparation of 4,4',4"-trihydroxytriphenylmethyl methane by condensing p-hydroxyacetophenone with phenol using a metal halide or acid catalyst. It is also known to react salicylaldehyde with certain phenolic compounds to obtain 4,4',2"-trihydroxyphenyl methanes. See, e.g., Beilstein EII6, pp. 1111-2; EIV6, pp. 7630-1; and EIV6, pp. 7643-4.
It is known to prepare a 4,4',4"-methylidyne tris(2,6-dimethylphenol) by reacting ethyl orthoformate (triethoxy methane) with the magnesium bromide Grignard reagent of 2,6-dimethylphenol. Chemical Abstracts 68:12811g. Said method employs relatively expensive starting materials, and requires special care since Grignard reagents react rapidly with both water and oxygen.
Heretofore, 4,4',4"-methylidyne tris(2,6-dimethylphenol) and related tris(p-hydroxyphenyl)methanes have not been prepared from the relatively inexpensive salicylaldehyde and its derivatives.